The long-term goals of this research project are to develop eppin as a male contraceptive target. We have been studying the interaction of eppin with semenogelin on the human sperm surface, particularly with regard to the resumption of sperm motility following ejaculation. Since our publication in Science in 2004 on the complete and reversible contraception of male monkeys immunized to a high titer with eppin, we have been investigating eppin as a drugable target. This application presents the detailed steps necessary for developing a drugable compound that inhibits eppin semenogelin binding. When eppin semenogelin binding is blocked, sperm motility is effectively inhibited. This project will be in conjunction (subcontract) with the drug discovery research program at the BRITE center, NCCU.
Specific aim #1 is the identification of novel, potent and highly specific inhibitors of eppin-semenogelin binding through directed library screening (hit generation). Based on our preliminary data on compound A4, this aim will test the hypothesis that more potent and specific inhibitor compounds of eppin-semenogelin binding can be identified. To identify inhibitors in this specific aim, 3 development units will be established to coordinate the research flow at the BRITE Center: (1) Assay Development Unit, (2) Assay Implementation Unit (3) Screening and HTS Unit.
Specific aim #2 is the iterative improvement of initial hits identified in Specific Aim #1 with medicinal chemistry and molecular modeling (hit-to-lead optimization) to improve the potency, selectivity and cell permeability and to decrease the cell toxicity.
Specific aim #2 will establish 2 working units: (1) The Chemistry Unit and (2) The Cheminformatics Unit.
Specific aim #3 will better define the target site on eppin for semenogelin and compounds discovered in specific aims #1 and #2. Using the eppin-semenogelin in vitro assays, recombinant eppin protein fragments and eppin with mutated key amino acid residues will be used to better define the semenogelin (or compound, e.g., A4) binding site on eppin.
This specific aim will test the hypothesis that defining exactly which eppin amino acids are essential for semenogelin and/or a target compound binding will enable us to refine the specificity of the compound.

Public Health Relevance

This research project seeks to develop a new non-steroidal male contraceptive that will allow males greater choices than condoms or vasectomy. Wide spread availability of male contraceptives will enhance family planning throughout the world.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project--Cooperative Agreements (U01)
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Special Emphasis Panel (ZHD1-DSR-L (08))
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Lee, Min S
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University of North Carolina Chapel Hill
Schools of Medicine
Chapel Hill
United States
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O'Rand, Michael G; Widgren, Esther E (2012) Loss of calcium in human spermatozoa via EPPIN, the semenogelin receptor. Biol Reprod 86:55
O'Rand, Michael G; Widgren, Esther E; Hamil, Katherine G et al. (2011) Epididymal protein targets: a brief history of the development of epididymal protease inhibitor as a contraceptive. J Androl 32:698-704
O'Rand, Michael G; Widgren, Esther E; Hamil, Katherine G et al. (2011) Functional studies of eppin. Biochem Soc Trans 39:1447-9
Mitra, Anurag; Richardson, Richard T; O'Rand, Michael G (2010) Analysis of recombinant human semenogelin as an inhibitor of human sperm motility. Biol Reprod 82:489-96